Various electronic devices and systems are designed to operate at cryogenic temperatures, well below liquid nitrogen temperatures. Infrared sensors, demagnetization devices, infrared interferometers, cryogenic optics and filters, and low noise cryogenic electronic devices are representative electronic components that require cooling at cryogenic temperatures. For applications of short duration, cryogenic dewars are useful for providing cryogenic cooling to such electronic components and other devices. However, a closed loop refrigeration system is required for applications that must be conducted intermittently or continuously over a long period of time, such as certain spacecraft experiments, interplanetary missions, and processing and manufacturing in space.
Closed cryogenic cooling systems typically employ a Joule-Thomson flow restrictor to reduce the temperature of a cryogen such as hydrogen, helium, nitrogen, oxygen, air, or methane. The cryogenic gas is typically compressed and then cooled to well below its inversion temperature in a regenerative heat exchanger prior to being adiabatically expanded through the Joule-Thomson flow restrictor. The expansion can be made to liquify part of the gas. The expanded gas is recirculated in a closed loop through a compressor of conventional design. See U.S. Pat. No. 3,415,077; U.K. Pat. No. 1,433,727; Lerner, E., et al., Cryogenics, pp. 548-550, September 1975. Mechanical compressors are considered unreliable for long-term and intermittent applications, making them unsuitable for spacecraft applications. A cryogenic refrigeration system with no moving parts would enhance the operating lifetime and reliability of cryogenically cooled electronic components sent into deep space and other environments where maintenance is impossible or impractical. Recently, molecular absorption compressors have been incorporated into closed cryogenic cooling systems containing only a few moving parts, but the metal halide pumps must be staged to achieve the compression and in addition require sophisticated feedback control. See AIAA Papers Nos. 82-0830 and 84-0058.
Electrochemical pumps, described for example in U.S. Pat. Nos. 3,489,670 and 4,118,299, typically compress hydrogen by transporting hydrogen ions across a solid polymer membrane containing water in some form.